Neuroleptics and anticholinergics are often used in combination for the treatment of schizophrenia, often at variance with rational guidelines. Little is actually known about the interaction of these two classes of drugs and the impact of the anticholineric agent on serum neuroleptic levels, clinical response, or hormonal response (e.g. Prolactin). This study will investigate the haloperidol/benztropine mesylate interaction by utilizing a double-blind crossover design in 40 schizophrenics. Serum levels of both drugs will be assayed. Prolactin levels will also be assayed as an in vivo test for dopamine receptor blackade. Clinical response and extrapyramidal side effects will be monitored. Analysis of the data will provide valuable information about the interaction of this common drug combination.